1. Field of the Invention
The present invention relates to an instrument for an endoscope such as a high frequency knife for resecting living tissues, in particular, a high frequency knife used for endoscopic submucosal dissection (hereinafter abbreviated as “ESD”), and also to an instrument system for an endoscope having the instrument for an endoscope.
2. Description of Related Art
Treatments for resecting living tissues such as mucosa using endoscopes have been performed conventionally and ESD such as resecting lesions formed on the surface of the digestive tract by dissecting submucosa to resect the affected area after circumferential incision of normal mucosa in the outer side of the affected area has been carried out.
When carrying out ESD, bleeding often occurs when circumferentially incising mucosa or exfoliating submucosal layer. Therefore, there is a need to perform procedures while carrying out dissection treatment and bleeding coagulation treatment alternately at appropriate timing.
When dissection of living tissue is carried out, the living tissue is locally cauterized and dissected by applying high frequency current (current for dissection) to an electrode section such as a scalpel whose contact area with the living tissue is small. On the other hand, when performing coagulation treatment for bleeding, the bleeding site and the living tissue around it is cauterized to carry out blood coagulation procedures by applying a current different from the one applied at the time of dissection (current for coagulation) to an electrode section with a shape such as of a sphere whose contact area with the living tissue is large.
As described so far, it is necessary to apply currents with different frequencies (waveforms) to electrode sections with different shapes in order to carry out dissection and coagulation treatments.
Although it is possible to apply currents for dissection and coagulation respectively to one electrode section, when applying the current for coagulation to an electrode section such as a scalpel with a small contact area with the living tissue, there is a concern that resection may be carried out without coagulation because of high energy density. On the other hand, when applying the current for dissection to an electrode section with a large contact area with the living tissue, resection may be impossible due to low energy density.
Accordingly, as described above, it is necessary to use two electrode sections which are different from each other for carrying out dissection and coagulation treatments, respectively.
Thus, conventionally, in order to perform dissection and coagulation treatments during ESD, there has been no alternative but to use an instrument for dissection and an instrument for coagulation having respective electrode sections at distal ends thereof alternately by interchanging them in the channel of endoscope.
Accordingly, it inevitably takes time to exchange the instruments and the procedures take more time, resulting in heavy burden on the patients. Moreover, it has been difficult to perform rapid hemostasis treatment at the bleeding site because of the time spent until the coagulation treatment is carried out.
Thus, an electrode rod for resection (refer to patent document 1, for instance) capable of shortening the time spent on dissection and coagulation treatments, a single pole polyp resecting snare provided with a coagulation electrode (refer to patent document 2, for instance), and the like are known for resolving such inconveniences.
The electrode rod for resection described in patent document 1 is equipped with electrodes for both dissection and coagulation at the distal end of the main body thereof. Therefore, it is possible to apply current to both electrodes simultaneously by applying current to a conducting section provided on the proximal end side of the electrode rod main body. It is possible to carry out dissection and coagulation treatments rapidly by making the respective electrodes contact the living tissue alternately.
In addition, the single pole polyp resecting snare provided with a coagulation electrode described in patent document 2 is equipped with a ring-shaped surface electrode (electrode for coagulation) with a large contact area with the living tissue at the distal end of a tubular plastic member. Moreover, it is provided with a conductive snare loop (electrode for dissection) arranged so as to be freely movable forward and backward inside the plastic member and capable of ligating living tissues. Furthermore, the surface electrode and loop are electrically connected to cords having plugs at their ends so as to be connectable separately to jacks of their electrosurgical oscillator.
According to this single pole polyp dissecting snare provided with a coagulation electrode, rapid dissection and coagulation treatments can be carried out by merely exchanging plugs connected to respective cords of the surface electrode and loop to the jacks of an electrosurgical oscillator.
[Patent Document 1] Japanese Unexamined Patent Application, First Publicaion No. Sho 55-125858
[Patent Document 2] Japanese Unexamined Patent Application, First Publicaion No. Hei 5-337130
However, the problems below remained unresolved with the inventions described in the above patent documents 1 and 2.
When the current is applied to the conductive section in the electrode rod for resection described in patent document 1, the current is applied to the electrode sections for both dissection and coagulation. Accordingly, for instance, there is the possibility of damaging untargeted parts when the electrode section for dissection unexpectedly contacts living tissue while carrying out blood coagulation at the bleeding site. Therefore, it is hard to use and puts excessive strain on the operator. In addition, it is impossible to apply current with different frequencies to the electrode sections for dissection and coagulation, and there is the concern of inappropriate dissection or blood coagulation treatment.
On the other hand, although it is possible to solve the aforementioned disadvantages by using the single pole polyp resecting snare provided with a coagulation electrode described in patent document 2, there is a need to exchange plugs plugged into the electrosurgical oscillator every time the surface electrode or loop is used. Accordingly, although not as much as when exchanging instruments, it is still laborious to exchange jacks resulting in the inconvenience of longer hours spent for ESD. Thus, there is a heavy burden on the patient.
The present invention was made by taking the aforementioned problems of the prior art into consideration and its object is to provide an instrument for an endoscope and an instrument system for an endoscope which make it possible to perform dissection and coagulation treatments by rapidly using electrode sections with appropriate shapes for each purpose separately, which require less labor, and also capable of reducing the burden on the patient by shortening the time spent for the procedures.